Forty-seven people were killed and a large swath of downtown was destroyed on July 6, 2013, when an unmanned 72-car train jumped the track, spilling and igniting some six million litres of volatile crude oil.
At noon, people gathered outside Lac-Megantic's St-Agnes Church for a moment of silence and a ringing of the bells. Ongoing decontamination work was also halted briefly to mark the tragedy.
A low-key mass was held Sunday night.
Politicians of all stripes marked the anniversary, vowing to continue to support the community.
Premier Philippe Couillard hailed the resolve of locals and said in a statement the province would keep helping the town of 6,000.
"Our thoughts are with the families and relatives of the victims and to all citizens of Lac-Megantic," Couillard said. "The Meganticois are a good example of solidarity and resilience for all of Quebec."
Prime Minister Stephen Harper also praised residents as the town rebuilds and heals.
"It takes people of extraordinary strength to overcome such a disaster, and I was privileged to witness first-hand during my visits to Lac-Megantic the remarkable resilience, pride and spirit of those in the community," Harper said.
He added that those found guilty of breaking the law will be held to account.
In late June, several people and the defunct rail company at the heart of the disaster were hit with new federal charges. Among the accused were Montreal, Maine and Atlantic Railway, the insolvent company's former president, and train driver Thomas Harding.
All those charged will appear in court in Lac-Megantic on Nov. 12.
Previously, Harding, two fellow railway employees and the company were charged by the Crown in Quebec with 47 counts of criminal negligence causing death. A trial date is expected to be set Sept. 8.
NDP Leader Tom Mulcair and Liberal Leader Justin Trudeau also marked the anniversary and both said not enough has been done.
"Every possible precaution must be taken to ensure such an incident is never repeated," Trudeau said. "Unfortunately, two years have passed and too little has been done by this government to bring about the necessary changes."
Mulcair said the NDP called in January for an independent investigation into transportation of dangerous goods by rail. He said he'd grant a costly solution being sought by the city.
"An NDP government would build a railway bypassing Lac-Megantic, which has already paid a high price in human lives," Mulcair vowed.
Transport Minister Lisa Raitt defended the government's actions, including stricter rules and lower speed limits for trains carrying dangerous cargo through urban areas.
In March, the government announced proposed new federal regulations that would give companies until 2025 to upgrade rail tank cars to a higher safety standard.
"Safety is Transport Canada’s top priority," Raitt said. "And in the wake of the accident, we took immediate, concrete action to further protect Canadians and maintain the safety and integrity of the Canadian rail system."
Lac-Megantic residents are also waiting to hear the fate of a court settlement, where about 25 companies accused of responsibility have put up a fund of $431.5 million.
The settlement is being opposed by the only firm that hasn't signed on: Canadian Pacific Railway Ltd. (TSX:CP).
If the legal challenge fails, lawyers representing victims and creditors hope money can start being disbursed later this year.